ATi RADEON - The Empire strikes back (3/15)

Lets take a look at the RADEON’s 3D features. As I mentioned, this list is quite long. These are the highlights:

Charisma Engine

ATi is grouping several features together under this name. The most important is probably the T&L implementation. Taking its cue from NVIDIA, ATi is also calling it a "GPU" (Graphics Processing Unit). This means that it renders Transformation and Lighting in the chip’s hardware to allow for scenes with a much higher polygon count and therefore much higher complexity and level of realism. Clipping is also supported in hardware.

Next on the list is Skeletal Animation und Skinning, adding the capability to move a hierarchically organized composite 3D object without having to rely on the CPU. This is similar to the GeForce2’s vertex skinning, but while NVIDIA settles for 2-matrix blending, RADEON can use up to 4 matrices. It should be noted however, that 3 matrices are theoretically sufficient to render even complex objects without glitches. Due to its 2-matrix limitation, the GeForce2 has to fall back on the CPU more often than the RADEON when rendering complex bone structures. The GF2 does not support skeletal animation in hardware.

That brings us to the next highlight - Vertex Morphing. This works just like a 2D morpher. Give it a starting and an ending position to modify a 3D object and the hardware will fill in the frames between these two "keyframes". ATi's example is a smirking face that turns into a sad one.

Another new addition to the feature set are so-called 3D Textures, which have a wide range of applications. Normal 3D objects are hollow. If you were to cut through a tube or pipe in a 3D environment, you’d be able to look into the two resulting halves. If you want to prevent this, several more processing/rendering steps are needed – one to re-close the opened pipe, and another to add a texture onto it (ähh, so ungefähr richtig?? -BEN). In comparison, if such an object were created using a 3D texture, the open sections would automatically be sealed. According to ATi, the upcoming Team Fortress 2 will be using 3D textures. Don’t expect to see complex effects as far as depth of field are concerned, however. These will most likely be handled by simpler means like different color intensities (i.e. the shimmering aura around a lightsource) or mathematical or procedural textures. So this implementation is still a far cry from being a real volumetric renderer.

Team Fortress 2 will be using 3D textures. Note the shimmering around the lightsource in the left picture

RADEON will offer support for all currently available forms of bump mapping. This means that in addition to the "common" Emboss bump mapping, the more complex DOT3 BM favored by NVIDIA and Matrox’s Environmental BM will also be supported. On top of that, ATi has built in a fourth kind of texture mapping, called Projective Textures. These work like a film projector, projecting a texture onto a plane. The advantage of this technique is that it can draw a moving object in front of a static texture while displaying the texture on the moving object. Imagine someone walking in front of the movie screen at your movie theater while the film is running and you’ve got the picture. The list of mapping techniques also includes Cube Environment Mapping (well known from GeForce), Spehercial Environment Mapping and Dual Paraboloid Environment Mapping. And last but not least, there are Shadow Mapping and Range-Based Fog. Quite an impressive list!

You can find more in-depth information on ATi Homepage.

Copyright: 07.08.2000 -   RIVA Station 2000 - Lars Weinand
No Copy without Permission!

Translation by Benjamin Kraft

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